Friday, 26 June 2009

U.S. Energy Statistics

Energy Statistics is not an exact science and the more detailed information you seek, the more difficult it gets. Making estimates of national energy comsumption, and even energy consumption per sector, based on information from energy importers and distributors, seems to be a fairly straightforward matter of collecting and compiling available data. But when it comes to detailed splits of how this energy is used in each sector it gets a lot more complicated, time consuming and costly, especially in the domestic sector, as this requires surveying thousands of homes, in order to get a decent average of typical household energy use, as described here: Survey Methods

The official source of U.S. energy statistics, the Energy Information Agency has not published any new detailed household data since 2001 because it is so difficult to make correct estimates for such a large country with such varying climate zones, housing types and economic conditions. But as percentages often stay somewhat similar within a decade - unless something unusual occurs - the available data may still give a reasonably correct estimate even part of it is somewhat dated. (I've been informed that it is more important for accuracy to stick to the same source than to the same year, as different agencies may measure in different ways and include different things in their calculations.)

All sectors

- U.S. share of world primary energy use 2006: 21.1% [1]

- Total U.S.energy consumption 2008: 99.3 quadrillion Btu (British thermal units) [2]
End-use sector shares of total consumption 2008 [3]:
- Residential (private homes) 22%
- Commercial 19%
- Industrial 31%
- Transportation 28%


Residential sector

A. Applying the proper hierarchies (see my first post about energy statistics) we get the following picture by combining the available data from EIA:

- Total U.S. energy consumption 2008: 99.3 qBtu [2]
- Residential energy consumption 2008: 21.64 [2]
- Residential electricity consumption 2008: 4.71 [4]
- Lighting part of household electricity 2001: 8.8% [5] = 0.42 qBtu = 1.94% of household energy consumption or 0.42% of total U.S. energy consumption.

B. But not all household lamps are incandescent, as many have already switched to halogen, CFL or LED. In 2001, the incandescent percentage of household lighting was around 95%. Today it is estimated by EIA at around 70% and CFL at around 20%. Plus, many have dimmers and sensors installed and may already have cut their incandescent lighting consumption. But let's say 70% for simplicity's sake = 1.36% of residential energy consumption, or 0.32% of national energy consumption.

C. Of these 1.36%, CFL proponents hope to save 75% = 1.02% of residential energy comsumption. But, as shown under CFL Analysis - Savings Summary, the average CFL savings are realistically probably closer to 50% than 75% (especially if you include the covered CFL bulbs with lower output and all the cheap CFLs that do not meet EnergyStar standards) = 0.68% of household energy consumption, or 0.16%of national.

D. Not all of the incandescents left will be suitable for replacement. This can be due to luminaire restrictions (e.g. downlight or reflector); to the need for perfect colour rendering, immediate switch-on, sparkling effect or a relaxing, attractive light environent; to vision problems, hypersensitivity to UV or other medical reasons; or to plain dislike for the medocre light quality of CFLs.

E. When switching to energy saving lights, it's easy to start using more light instead, or to leave them on for longer, thinking energy savers use so little anyway (see Jevons paradox) or because the recommendation is to not turn CFLs on-and-off too frequently. Article comment to illustrate: "My dad switched to CFLs, but now he just leaves the lights on all the time because he says 'they use so little power, I can’t be bothered to turn them off'." Many CFLs are also supposed to be turned on for 15 minutes to 3 hours at a time in order not to shorten their life dramatically.

So, in reality, the potential savings we're talking about are in the order of up to 0.68% of total residential energy use or 0.16% of total U.S. energy consumption, probably less when taking D into consideration, and possibly none considering E.

Does this strike anyone as chasing very small drops in a very large energy ocean, while the BIG energy consumers: heating & cooling, water heating, transportation, commerce and industry can continue using up the remaining 99+% in peace as everyone thinks they've saved the planet by buying a few CFLs?

Commercial sector

- Total U.S. energy consumption 2008: 99.3 QBtu [2]
- Commercial energy consumption 2008: 18.54 QBtu [2]
- Commercial electricity consumption 2008: 4.61 QBtu [4]
- Lighting* part of commercial electricity 2003: 37.6% [6] = 1.34 Qbtu = 7.22% of commercial energy consumption or 1.35% of national.
*Including public street and highway lighting

There are many ways of calculating the percentage of each lamp type being used in commercial buildings: annual lamp sales; annual luminaire sales; current existence of different luminaire types, lumen-hours per year and lamp type, lit floor space, energy consumption per lamp type in Btu, in kWh etc. Finding recent info that goes into such details is difficult. Here is just one example, which may be still be reasonably representative (though most likely some incandescents are already replaced by CFLs):

Approximate percentage of lit floor space in commercial (non-mall) buildings 2003 [7]:
FL & CFL 74%
HID 9%
Incandescent 10%
Halogen 4%

So, even though lighting uses a larger percentage of the electricity consumption in the commercial sector, the incandescent part is so small - and shrinking - that replacing the few that are left is not going to make much of a difference energy-wise, only ruin the romantic atmosphere in restaurants, clubs, hotels and museums. (Offices rarely use incandescent lamps, except possibly a few in executive, reception or recreation areas, where their softer light may be needed.)

The greatest savings on lighting can probably be done by:

1. Upgrading existing poor quality FL tubes and luminaires in commercial buildings to T8 tri-phosphor tubes with electronic ballaststo metal halide spots/downlights or to LED spots/downlights.

2. Adjusting illuminance levels downwards in offices (as less light is needed when working online, than was needed when most office work consisted of physical paper work) and giving more individual control to users so they can turn down or off lights when not needed.

3. Using occupancy sensors and turning most office lights off at night.

4. Phasing out inefficient and poor-quality high-pressure mercury HID street lamps, replacing them with ceramic metal halide.  

5. Switching to LED traffic signals.

None of which requires banning incandescent lamps.

References:

1. EIA: Annual Energy Review 2008 (p. 348) Figure 11.3
2. EIA: Annual Energy Review 2008 (p. 41) Figure 1.0
3. EIA: Annual Energy Review 2008 (p. 76) Figure 2.1a
4. EIA: Annual Energy Review 2008 (p. 263) Figure 8.0
5. EIA: End-Use Consumption of Electricity 2001
6. EIA: Annual Energy Review 2008 (p. 102) Figure 2.11
7. EIA: Lighting in Commercial Buildings 2003 Table 1

7 comments:

  1. Great Site! I've linked to your blog at greencomplianceplus.markenglisharchitects.com. Thanks again, I'll be reading your work.

    ReplyDelete
  2. Re U.S. Energy Information Administration stats....
    funny then how energy secretary Chu choose to ignore his own stats yesterday!

    he and obama made a point yesterday of they want to ban light bulbs..
    eg. CBS news (+comments! )

    and I was having such a nice midsummery night slumber!...
    http://www.ceolas.net/#li1x onwards all(?) the reasons against a ban

    ReplyDelete
  3. Rebecca, thanks. :-)

    Panta Rei, thanks for the link.

    They could be right though...

    "I know light bulbs might not seem sexy," Mr. Obama said, "but this simple action holds enormous promise because 7 percent of all energy consumed in America is used to light our homes and our businesses."

    Note "homes AND businesses". Businesses probably use over 6 of those possibly 7% lighting - most of which is already FL, some HID and, a smaller part halogen, rather than incandescent. Lumping them together like that is a great way of making it seem like more than it is witout actually lying. This is what PR-people get paid to do.

    Seems like the lighting lobby must have gotten to him too, despite his promises to restrict their influence. Possibly via naïve environmentalists who truly believe they're doing the right thing. *sigh*

    ReplyDelete
  4. Here's another good point re stats -
    he takes into account how lights are used in the house!

    http://papundits.wordpress.com/2009/07/02/light-bulb-regulation-president-fails-elementary-math/

    btw not all bad that obama made that announcement =
    it has woken people up, after all, the light bulbs were buried in the huge energy bill before, now suddenly people are talking about it....

    ReplyDelete
  5. Thanks for review, it was excellent and very informative.
    thank you :)

    ReplyDelete
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